Render curves as tubes?

Forums Technical Discussion Render curves as tubes?

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Anti-Distinctlyminty: Member; 271 posts; Joined: March 2012; Offline

Sept. 24, 2016 5:27 p.m.

Hi all,
I was wondering if I was missing something when it comes to render curves as tubes. I know that if you have a curve, you can set it's width attribtue and that will make it render as a strip. Then, using a hairNormal shader you can make it appear as a tube…ish. However, this is only a shader effect, so when it comes to rendering displacements on the tube, things can look pretty odd.
It is possible to render points as spheres, complete with actual geometry that can be displaced properly…but is this not possible with curves?


robsdesign: Member; 236 posts; Joined: March 2015; Offline

Sept. 25, 2016 8:19 a.m.

Hi, not sure if this is what you're after? (Using curve and sweep)

Attachments:
Curve_Tube.hiplc (49.3 KB)
Curve_Tube.jpg (81.5 KB)


BabaJ: Member; 2035 posts; Joined: Sept. 2015; Offline

Sept. 25, 2016 9:27 a.m.

Not sure if you can get a strip ‘shape’ with the polywire, but I haven't played with all the parameters on that node.

Maybe you can get more than a uniform polyshape and size from it.

Attachments:
Plywire example.hiplc (50.5 KB)


Anti-Distinctlyminty: Member; 271 posts; Joined: March 2012; Offline

Sept. 25, 2016 4:56 p.m.

I was thinking more along the lines of implicit tubes, but the replies I got over at odforce here [forums.odforce.net] just say that Mantra currently does not support this, which is a shame.

@robsdesign I tried using the sweep with nurbs, but the structure is quite large and the render times just went through the roof. I'm not sure why…maybe the combination of nurbs and displacement. In any case it's nmot usable

@BabaJ See above

I'm trying to keep to just implicit tubes from curves.

I'll put in and RFE for this.


mark: Staff; 2590 posts; Joined: July 2005; Offline

Sept. 26, 2016 8:05 a.m.

By default, mantra will shade just the centerline of the open curves. There's a setting to change it so that it shades curves as surfaces. I think vm_curvesurface is the setting. Memory will go up a little, but not as much as sweeping NURBs.


Anti-Distinctlyminty: Member; 271 posts; Joined: March 2012; Offline

Sept. 26, 2016 1:57 p.m.

mark
By default, mantra will shade just the centerline of the open curves. There's a setting to change it so that it shades curves as surfaces. I think vm_curvesurface is the setting. Memory will go up a little, but not as much as sweeping NURBs.

Hi Mark,
I have tried that, but the setting seems to make no difference.
I've attached my test scene, and you can see that the setting does not change the output.
Is there something I'm doing wrong here?


Anti-Distinctlyminty: Member; 271 posts; Joined: March 2012; Offline

Sept. 26, 2016 2:04 p.m.

…and the attachment.

Attachments:
displacement_sphere.hipnc (229.8 KB)


mark: Staff; 2590 posts; Joined: July 2005; Offline

Sept. 26, 2016 4:57 p.m.

Anti-Distinctlyminty
…and the attachment.

I won't actually have access to Houdini for a few days… You might have to do something “interesting” in the shader (interpolating normals based on t for example)


Anti-Distinctlyminty: Member; 271 posts; Joined: March 2012; Offline

Sept. 26, 2016 5:27 p.m.

Ah…I think we've come full circle. My original post was about how you can use the hair normal shader, but things can go a weird when you try to use displacements, but on a primitive sphere, everything works great as you get actual geometry

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